...IMO is Ann Wilson. IMHO there is no contest. That voice can move mountains and melt hearts...

Doro Pesch is very good too - a female Dio, really! In that vein Leather Leone (Chastain and also solo) is worth a mention. I don´t rate Pat Benatar, though some of her stuff is OK....There was a guest singer on the G3 Uli Jon Roth European tour who I think sang on one of his symphonic albums and she was really good, very Ann Wilson-esque. Anyone know any more?